共查询到19条相似文献,搜索用时 140 毫秒
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我国四类衬垫系统防污性能的比较分析 总被引:5,自引:0,他引:5
对我国填埋场采用的四类衬垫进行了防污性能的比较分析。评价参数包括渗漏率、污染物击穿时间及衬垫系统底部浓度值。除了2m压实黏土衬垫(CCL)外,其余3种均为包含土工膜(GM)的复合衬垫。分析模型采用了污染物通过有缺陷膜复合衬垫的一维运移解析解。以镉离子(Cd2+)为渗滤液中重金属离子的代表;以苯为其中挥发性有机污染物的代表。研究表明土工复合膨润土垫(GCL)复合衬垫的渗漏率最小,2m黏土最大,两者的差别可在3~5个数量级。GCL复合衬垫对重金属离子具有较好的防污性能,尤其是在高水头及复合衬垫接触较差的情形。厚度较大的2m黏土对挥发性有机污染物的防污性能较好,其击穿时间要比GCL复合衬垫大2~3个数量级。随着水头的增大,CCL复合衬垫的防污性能逐渐地优于2m黏土。在10m水头作用下,CCL复合衬垫底部的100年浓度可比2m黏土小近一个量级。单层膜衬垫的防污性能较差,不适合作为填埋场的衬垫系统。控制填埋场复合衬垫的施工质量和渗滤液水头尤为重要。 相似文献
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垃圾填埋场渗沥液击穿防渗系统的指示污染物研究 总被引:2,自引:0,他引:2
中国垃圾填埋场渗沥液中的污染物种类繁多,成分复杂,污染物击穿填埋场防渗系统,造成地下水以及土壤污染已成为填埋场环境安全问题中最为关注的问题之一。目前以什么标准判断击穿,以何种污染物作为指示污染物计算击穿时间并评价防渗系统的防污性能尚不明确。针对这一问题,以中国6个典型填埋场内代表性污染物的平均浓度为初始浓度,以中国相关环境标准中规定的各类污染物极限浓度作为污染浓度,建立污染物在复合防渗系统中的一维对流–弥散有限元模型。通过计算各类污染物在填埋场防渗系统中的击穿规律和击穿时间发现,相比重金属和持久性有机污染物,有机污染物(COD)最早击穿防渗系统,有机污染物(COD)可作为判定击穿的指示污染物,击穿HDPE土工膜单层和双层复合垫层的时间分别为84.2 a和122.6 a;而击穿时间主要受污染物的初始浓度、规定的污染浓度和污染物的迁移弥散参数共同影响。这一结果可为填埋场防渗系统击穿时间的计算和防污性能的评价提供参考。 相似文献
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为了解中国第一代垃圾填埋场中防渗帷幕的服役性能及其影响因素,以苏州七子山填埋场地质条件为例,以COD作为代表性污染物,在前期现场勘查基础上建立了有限差分计算模型,对防渗帷幕被污染物击穿时间的影响因素进行了计算分析,并基于Ogata解析解给出了防渗帷幕击穿时间和设计厚度的简化计算公式。模拟和分析结果表明:场地地质条件对嵌入式防渗帷幕击穿时间影响不十分显著;帷幕上下游水头差、帷幕渗透系数、阻滞因子和厚度对嵌入式防渗帷幕的击穿时间有显著影响,击穿时间与上下游水头差、帷幕渗透系数、阻滞因子、以及帷幕厚度的平方近似呈线性关系;扩散系数对嵌入式防渗帷幕击穿时间的影响不可忽略。 相似文献
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《岩土工程学报》2020,(10)
通过对中国6个典型垃圾填埋场中渗滤液各组分的实测浓度值的统计分析,并与中国生活饮用水卫生标准中的界限浓度值进行对比分析,确定了以渗滤液中不同污染物组分为指示性污染物时的典型击穿标准和极端情况的击穿标准分别为0.1和0.01。基于已有的污染物在复合衬垫GMB+CCL中的一维运移解析解,在分别考虑了以有机物污染物和无机污染物为击穿指标的情况下,利用数值拟合的方法得到了两种情况下复合衬垫中CCL厚度的简化计算公式。以杭州天子岭垃圾填埋场为例,利用简化计算方法对复合衬垫的厚度设计进行了验证;结果表明,若要保证渗滤液中的Pb击穿GMB/CCL复合衬垫的时间大于50 a,则土工膜下覆的CCL的厚度至少需要0.6 m。 相似文献
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卫生填埋场防渗层设置工程通常需要筹集大量的优质粘土.这对于许多地区是十分困难的.本文提出了以廉价复合土取代优质粘土的观点.并以普通粘土、伊利士和粉煤灰为对象进行了复合土防渗技术实验研究.结果表明:伊利土与粉煤灰复合后具有良好的抗渗性能,复合上在1.5g/cm3的密实度下可获得5.4×10-8m/s的渗透系数.粉煤灰在复合土中的最佳重量百分比范围是20%~30%. 相似文献
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粘土由于截污能力强、渗透系数小及价格经济等优势,被广泛应用于填埋场衬垫系统中。在渗流场和浓度场综合作用下,粘土衬垫不能完全隔绝污染物的向下扩散。当在土中施加直流电场时,污染物在电渗透和电迁移作用下向相反方向运动。本文根据水和离子在电场、渗流场和浓度场作用下的迁移原理研制了室内动电模拟试验装置,试验研究了多场耦合作用下锌离子在粘土中的迁移性状,并对试验结束后的土样进行了浓度,含水率及pH等测定。结果表明,动电作用可以有效地阻滞锌离子在粘土中的迁移。 相似文献
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旨在评价商用土工合成材料黏土衬垫(GCL)用于阻隔赤泥渗滤液的有效性。赤泥渗滤液作用下GCL的防渗特性是评价其防污性能的关键因素。以商用改性GCL中膨润土为研究对象,通过自由膨胀试验,研究了4种赤泥渗滤液中膨润土的自由膨胀指数。以商用改性GCL为研究对象,通过改进滤失试验,研究了4种赤泥渗滤液作为渗透液作用下GCL渗透系数的变化规律,评价了预水化作用对渗透系数的影响。研究还采用清洁自来水作为GCL的渗透液作为对照。结果表明,随着离子强度的增加,改性GCL中的膨润土自由膨胀指数随之减小。预水化处理改性GCL的渗透系数相较于未预水化处理试样降低了5倍左右。在实际工程应用中,建议采用自来水预水化处理GCL,以此充分发挥其防渗性能。随着改进滤失试验中施加气压的增大,不同赤泥渗滤液作用下的改性GCL渗透系数均下降。随着离子强度和一价二价离子摩尔数比的增加,改性GCL的渗透系数随之增大。随着膨润土自由膨胀指数的增加,改性GCL的渗透系数随之减小。与自来水渗透情况相比,赤泥渗滤液渗透作用下,改性GCL渗透系数增大4.35~12.0倍。 相似文献
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《Geotextiles and Geomembranes》2014,42(5):428-436
A one-dimensional model was developed to investigate the transport of organic acids (commonly found in landfill leachate) through a partially saturated composite liner system beneath a landfill. Specific attention was paid to the influence of water content distribution on aqueous-phase diffusion process. Composite liner system was investigated, which was consisted of a geomembrane and a compacted clay liner underlain by three kinds of attenuation layer: sand layer, sandy clay loam layer, and clay layer. Volumetric water content profile in soil layers was obtained by Van Genuchten model, and the Millington and Quirk model was employed to describe the non-linear relationship between volumetric water content and diffusion coefficient. Three cases were analyzed and compared, i.e., totally saturated condition, unsaturated condition without considering unsaturated diffusion model, and unsaturated condition considering unsaturated diffusion model. The numerical results show that the unsaturated sand attenuation layer could serve as excellent diffusion barrier to organic contaminant due to its low water retention capacity. When the dependence of diffusion coefficient on volumetric water content is sufficiently considered, the contaminant flux decreases significantly in all the three kinds of attenuation layer. Unsaturated diffusion model capturing the relationship between water content and diffusion coefficient enables a more reasonable prediction of contaminant transport and distribution in soils. 相似文献
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Huaxiang Yan Jiawei Wu Hywel R. Thomas Hao Ding Liangtong Zhan Haijian Xie 《Geotextiles and Geomembranes》2021,49(2):489-499
A triple-layer composite liner consisting of a geomembrane liner (GMB), a geosynthetic clay liner (GCL) and a compacted clay liner (CCL) is commonly used at the landfill bottom liner system to isolate the contaminated leachates. In this paper, one-dimensional quasi-steady-state small deformation model (SDSS) was developed to investigate the behavior of organic chemicals transport in landfill composite liner system considering coupled effect of consolidation, diffusion and degradation. The first and second type bottom boundary conditions are used to derive the analytical solutions. The generalized integral transform technique (GITT) is adopted to derive the analytical solutions. The effect of consolidation on the performance of GMB/GCL/CCL with intact or leaking GMB is investigated. The triple liner under double drainage boundary condition (DDBC) has better performance compared to the case under single drainage boundary condition (SDBC). This is because the velocity induced by consolidation under DDBC is lower than that under SDBC. The effect of GCL consolidation shows an opposite trend compared to CCL consolidation. Considering GCL consolidation can increase the breakthrough time. The effective diffusion coefficient of GCL can be two magnitude orders smaller after consolidation, which provides a better diffusion barrier for the chemical transport. The effects of adsorption and degradation have been analyzed as well. Increasing the adsorption capacity of a deforming composite liner can increase the steady-state bottom flux, which shows the opposite tendency compared to the case without considering consolidation. This is due to the fact that for the case of a deforming composite liner, the advection induced by consolidation includes a new term due to the solid velocity. This velocity will result in the increase the mass of chemical migration through the composite liner. 相似文献
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Shi-Jin Feng Ming-Qing Peng Hong-Xin Chen Zhang-Long Chen 《Geotextiles and Geomembranes》2019,47(3):282-294
In this study, analytical solution for degradable organic contaminant transport through a composite liner consisting of a geomembrane (GMB) layer, a geosynthetic clay liner (GCL) and an attenuation layer (AL) is derived by the separation of variables method. The transient contaminant transport in the whole composite liner can be well described avoiding some weird phenomena in existing analytical solutions. The results of parametric study show that GCL has significant effect on improving the barrier efficiency especially for scenarios with high leachate head. The biodegradation and adsorption in GCL have significant influence on the contaminant transport through the composite liner when the half-life of contaminant in GCL is less than 5 years. Otherwise, the effect can be neglected. 相似文献
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In municipal solid waste landfills, a triple-layer composite liner consisting of a geomembrane liner (GML), a geosynthetic clay liner (GCL) and a compacted clay liner (CCL) is commonly used at the landfill bottom to isolate the leachates from surrounding environment. This paper presents a numerical investigation of the effect of liner consolidation on the transport of a volatile organic compound (VOC), trichloroethylene (TCE), through the GML/GCL/CCL composite liner system. The numerical simulations were performed using the model CST3, which is a piecewise linear numerical model for coupled consolidation and solute transport in multi-layered soil media and has been extensively validated using analytical solutions, numerical solutions and experimental results. The performed numerical simulations considered coupled consolidation and contaminant transport with representative geometry, material properties, and applied stress conditions for a GML/GCL/CCL liner system. The simulation results indicate that, depending on conditions, consolidation of the GCL and CCL can have significant impact on the transport results of TCE (i.e., TCE mass flux, cumulative TCE mass outflow, and distribution of TCE concentration within the GCL and CCL), both during the consolidation process and long after the completion of consolidation. The traditional approach for the assessment of liner performance neglects consolidation of the GCL and CCL and fails to consider the consolidation-induced transient advection and concurrent changes in material properties and, therefore, can lead to significantly different results. These differences for with and without the consolidation effects can range over several orders of magnitude. The process of consolidation-induced contaminant transport is complex and involves many variables, and therefore case-specific analysis is necessary to assess the significance of liner consolidation on VOC transport through a GML/GCL/CCL composite liner system. 相似文献
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考虑填埋场中固体废弃物的生物降解效应和含水层中土颗料对污染物的吸附性,在有限深度条件下基于对流、弥散和地球化学反应等污染物运移机理,提出了填埋场污染物运移过程数值模拟的一维计算模型。进而采用半解析方法进行数值求解,通过变动参数比较分析确定了控制填埋场污染物运移过程的主要参数。具体数值计算表明:污染物在含水层中运移浓度将于某一特定时间达到峰值,随后逐渐降低。粘土垫的厚度及其渗透性、压缩粘土垫层与含水层的吸附能力是填埋场污染物运移的重要近控制参数。 相似文献
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In 2004, Chinese Government prescribed standard municipal solid waste (MSW) landfill bottom liners. However, very limited research has been conducted to evaluate the performance of the standard MSW landfill bottom liners prescribed by the Chinese Government. In this paper, the performance of the two types of Chinese MSW landfill bottom liner systems was evaluated based on: (1) the maximum leachate head; (2) leakage rate; (3) peak concentration of the target contaminant in an aquifer which was underlain the assumed landfill, and (4) total mass per unit area of the target contaminant discharged into the aquifer. The performance of the German standard MSW landfill bottom liner system was evaluated and compared with that of Chinese ones. It is found that the calculated maximum leachate head for the Chinese landfill liner systems was much higher than that for the German one. The calculated leakage rate, peak concentration and the maximum total mass per unit area in the aquifer of the target contaminant show that the performance of the Chinese standard landfill liner Type 2 is practically the same as that of the German standard landfill liner with holed geomembrane wrinkles, while the Chinese standard liner Type 1 is less effective, with regarding the mitigation of the impact of landfills to the groundwater quality. It is concluded that the overall performance of the Chinese standard landfill liner systems is less strict than that of the German standard landfill liner system. 相似文献
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Evaluation of interface shear strength of composite liner system and stability analysis for a landfill lining system in Thailand 总被引:2,自引:0,他引:2
The paper presents the case history of laboratory evaluation of the interface shear strength properties of various interfaces encountered in a modern day landfill with emphasis on proper simulation of field conditions and subsequent use of these results in the stability analyses of liner system. Over 70 large direct shear tests were systematically conducted to evaluate the interface shear strength properties of composite liner system using project specific materials under site specific conditions, being used at non-hazardous and hazardous landfills project situated in Sa Kaeo Province, Thailand. The critical interfaces were located between the geotextiles and the smooth geomembrane (GM), the smooth GM and the geosynthetic clay liner (GCL), and the smooth GM liner and the compacted clay liner (CCL) with the interface friction angles ranging from 6.5° to 10.5° for dry conditions and 6.5° to 9.5° in wet conditions. The residual shear stress for these interfaces was attained at a displacement less than 4 mm. Three methods, namely, limit equilibrium method (LEM), limit method (LM), and the simple composite column (SCC) approach were used to evaluate the tensile loads induced in the geosynthetic components. The SCC approach proposed by Liu, C.N. [2001. Tension of geosynthetics material regarding soils on landfill liner slopes. Proceedings, National Science Council ROC(A), 25(4), 211–218] that takes into account the force equilibrium as well as displacement compatibility yielded satisfactory results. The factor of safety for geosynthetic components in the liner was found to be greater than 3.0 for both types of landfill. 相似文献